/**
 * Settle a ROT/RUT begäran: book Skatteverkets utbetalning and, optionally,
 * link the bank transaction that carried it.
 *
 *   Debit  19xx bank account (default 1930)  [amount]
 *   Credit 1513 Skattereduktion rot/rut      [amount]
 *
 * Shared between two callers:
 *   - REST: app/api/rot-rut/payout-requests/[id]/settle/route.ts
 *     (headless settle: amount/date/bank account supplied by the caller)
 *   - REST: app/api/transactions/[id]/match-rot-rut-payout/route.ts
 *     (bank-row match: amount/date/bank account come from the transaction,
 *     and the row is linked to the settlement voucher in the same call)
 *
 * The journal entry IS the accounting record: engine failure blocks the whole
 * operation. Everything after the voucher is best-effort-with-loud-logging,
 * never an unbook (the voucher is immutable per BFL).
 */
import type { SupabaseClient } from '@supabase/supabase-js'
import { createRotRutPayoutEntry } from '@/lib/bookkeeping/rot-rut-entries'
import { clearSettledInvoiceSuggestions } from '@/lib/invoices/clear-settled-invoice-suggestions'
import { logMatchEvent } from '@/lib/invoices/match-log'
import { propagateUnderlagForBookedTransaction } from '@/lib/transactions/inbox-underlag'
import { roundOre } from '@/lib/money'
import { createLogger } from '@/lib/logger'

const log = createLogger('invoices/rot-rut-settle')

export interface SettleRotRutPayoutParams {
  requestId: string
  paymentDate: string
  /** Defaults to decided_total ?? requested_total. */
  amount?: number
  /** BAS 19xx account the payout landed on. Defaults to 1930 in the engine. */
  bankAccount?: string
  /**
   * Bank transaction that carried the payout. When set, the row is linked to
   * the settlement voucher (journal_entry_id) and its match hints are cleared.
   * The caller must have verified the row is unbooked and belongs to the
   * company; this function re-checks with an optimistic lock on
   * journal_entry_id IS NULL.
   */
  transactionId?: string
  /**
   * The transaction's journal_entry_id as the caller read it: null for a free
   * row, or the STALE id of a reversed/cancelled entry the route judged not
   * live (issue #988). The link CAS locks on exactly that value, so a stale
   * pointer can be overwritten while a concurrent live link still turns the
   * write into a no-op (same contract as link-journal-entry.ts).
   */
  previousJournalEntryId?: string | null
}

export interface SettledRotRutPayoutRequest {
  id: string
  name: string
  deduction_type: 'rot' | 'rut'
  status: string
  requested_total: number | string
  decided_total: number | string | null
  decided_at: string | null
  settlement_journal_entry_id: string | null
}

export type SettleRotRutPayoutErrorCode =
  | 'ROT_RUT_REQUEST_NOT_FOUND'
  | 'ROT_RUT_SETTLE_INVALID_STATE'
  | 'ROT_RUT_SETTLE_AMOUNT_EXCEEDS'
  | 'ROT_RUT_SETTLE_RACE'
  | 'ROT_RUT_MATCH_TX_LINK_FAILED'

export type SettleRotRutPayoutOutcome =
  | {
      ok: true
      request: SettledRotRutPayoutRequest
      journalEntryId: string
      amount: number
      fullyPaid: boolean
    }
  | { ok: false; kind: 'code'; code: SettleRotRutPayoutErrorCode; details?: Record<string, unknown> }
  /** A raw Supabase/engine error the route maps through errorResponse(). */
  | { ok: false; kind: 'error'; error: unknown; stage: 'fetch' | 'book' | 'update' }

export async function settleRotRutPayoutRequest(
  supabase: SupabaseClient,
  userId: string,
  companyId: string,
  params: SettleRotRutPayoutParams,
): Promise<SettleRotRutPayoutOutcome> {
  const { data: payoutRequest, error: fetchError } = await supabase
    .from('rot_rut_payout_requests')
    .select('*')
    .eq('company_id', companyId)
    .eq('id', params.requestId)
    .maybeSingle()

  if (fetchError) {
    return { ok: false, kind: 'error', error: fetchError, stage: 'fetch' }
  }
  if (!payoutRequest) {
    return { ok: false, kind: 'code', code: 'ROT_RUT_REQUEST_NOT_FOUND' }
  }

  const settleable =
    !payoutRequest.settlement_journal_entry_id &&
    !['cancelled', 'rejected'].includes(payoutRequest.status)
  if (!settleable) {
    return {
      ok: false,
      kind: 'code',
      code: 'ROT_RUT_SETTLE_INVALID_STATE',
      details: {
        status: payoutRequest.status,
        already_settled: !!payoutRequest.settlement_journal_entry_id,
      },
    }
  }

  const amount =
    params.amount ?? Number(payoutRequest.decided_total ?? payoutRequest.requested_total)

  // A partial settlement must follow a recorded beslut: without this guard a
  // settle with amount < requested_total on an undecided request would flip
  // it to partially_paid while bypassing the PATCH lifecycle rule that
  // partially_paid requires decided_total: the beslut would never be
  // recorded and later PATCH calls would be blocked by ALLOWED_TRANSITIONS.
  if (amount < Number(payoutRequest.requested_total) && payoutRequest.decided_total == null) {
    return {
      ok: false,
      kind: 'code',
      code: 'ROT_RUT_SETTLE_INVALID_STATE',
      details: {
        status: payoutRequest.status,
        reason:
          'Delutbetalning kräver att Skatteverkets beslut registreras först (decided_total via PATCH).',
      },
    }
  }

  // Never book more than Skatteverket can owe on this begäran: a larger bank
  // row (a moms/skattekonto refund, two begäran in one transfer) would drive
  // 1513 into a credit balance and rewrite decided_total to the bank amount.
  // The user books such a row another way; this path stays exact.
  const expectedAmount = roundOre(Number(payoutRequest.decided_total ?? payoutRequest.requested_total))
  if (amount > expectedAmount + 0.005) {
    return {
      ok: false,
      kind: 'code',
      code: 'ROT_RUT_SETTLE_AMOUNT_EXCEEDS',
      details: { amount, expected_amount: expectedAmount, status: payoutRequest.status },
    }
  }

  // The voucher is the accounting record: engine failure must block.
  let journalEntryId: string
  try {
    const entry = await createRotRutPayoutEntry(supabase, companyId, userId, {
      requestId: payoutRequest.id,
      requestName: payoutRequest.name,
      deductionType: payoutRequest.deduction_type,
      paymentDate: params.paymentDate,
      amount,
      bankAccount: params.bankAccount,
    })
    journalEntryId = entry.id
  } catch (engineError) {
    return { ok: false, kind: 'error', error: engineError, stage: 'book' }
  }

  const fullyPaid = amount >= Number(payoutRequest.requested_total)
  const update: Record<string, unknown> = {
    settlement_journal_entry_id: journalEntryId,
    status: fullyPaid ? 'paid' : 'partially_paid',
    decided_total: payoutRequest.decided_total ?? amount,
  }
  if (!payoutRequest.decided_at) {
    update.decided_at = new Date().toISOString()
  }

  // CAS on settlement_journal_entry_id IS NULL: two concurrent settles (two
  // same-amount bank rows, or a headless call racing a match) must not both
  // attach and credit 1513 twice. The loser's voucher already exists
  // (immutable per BFL): say so loudly rather than overwrite the winner.
  const { data: updated, error: updateError } = await supabase
    .from('rot_rut_payout_requests')
    .update(update)
    .eq('company_id', companyId)
    .eq('id', params.requestId)
    .is('settlement_journal_entry_id', null)
    .select(
      'id, name, deduction_type, status, requested_total, decided_total, decided_at, settlement_journal_entry_id',
    )
    .maybeSingle()

  if (updateError) {
    // The voucher exists (immutable per BFL) but the request row didn't
    // absorb the link: surface loudly, do NOT try to unbook.
    log.error('rot/rut payout entry booked but request update failed', updateError, {
      journalEntryId,
      payoutRequestId: params.requestId,
    })
    return { ok: false, kind: 'error', error: updateError, stage: 'update' }
  }
  if (!updated) {
    log.error('rot/rut payout entry booked but request was settled concurrently', undefined, {
      journalEntryId,
      payoutRequestId: params.requestId,
    })
    return {
      ok: false,
      kind: 'code',
      code: 'ROT_RUT_SETTLE_RACE',
      details: { journal_entry_id: journalEntryId, request_id: params.requestId },
    }
  }

  if (params.transactionId) {
    // Optimistic lock on the pointer the route read: null for a free row, or
    // the stale id of a reversed entry (issue #988) that the route judged not
    // live. A concurrent booking between that read and this write changes
    // the pointer, so the write matches 0 rows instead of silently
    // overwriting it (same CAS contract as link-journal-entry.ts).
    const previousJournalEntryId = params.previousJournalEntryId ?? null
    const txUpdate = supabase
      .from('transactions')
      .update({
        journal_entry_id: journalEntryId,
        is_business: true,
        category: 'income_other',
        potential_invoice_id: null,
        potential_supplier_invoice_id: null,
        potential_rot_rut_payout_request_id: null,
        // The match supersedes any prior reconciliation link (mirrors
        // match-invoice): a literal null keeps the phantom-column scanner
        // able to verify the column set.
        reconciliation_method: null,
      })
      .eq('id', params.transactionId)
      .eq('company_id', companyId)
    const { data: linkedRows, error: linkError } = await (previousJournalEntryId === null
      ? txUpdate.is('journal_entry_id', null)
      : txUpdate.eq('journal_entry_id', previousJournalEntryId)
    ).select('id')

    if (linkError || !linkedRows || linkedRows.length === 0) {
      // Voucher booked and request settled, but the bank row is not linked:
      // the user can still attach it via "Matcha mot befintlig verifikation".
      // Say exactly that instead of pretending the match went through.
      log.error('rot/rut payout settled but transaction link failed', linkError ?? undefined, {
        journalEntryId,
        payoutRequestId: params.requestId,
        transactionId: params.transactionId,
        reason: linkError?.message ?? 'optimistic lock returned 0 rows',
      })
      return {
        ok: false,
        kind: 'code',
        code: 'ROT_RUT_MATCH_TX_LINK_FAILED',
        details: { journal_entry_id: journalEntryId, request_id: params.requestId },
      }
    }

    // An utbetalningsbesked pinned on the bank row becomes the voucher's
    // underlag (BFL 5 kap 6 §), as every other booking path does.
    await propagateUnderlagForBookedTransaction(
      supabase,
      companyId,
      params.transactionId,
      journalEntryId,
    )

    await logMatchEvent(supabase, userId, params.transactionId, 'matched', {
      matchConfidence: 1.0,
      matchMethod: 'rot_rut_payout_manual_confirm',
      newState: {
        journal_entry_id: journalEntryId,
        rot_rut_payout_request_id: params.requestId,
        request_status: update.status,
        amount,
      },
    })
  }

  if (fullyPaid) {
    const { data: items, error: itemsFetchError } = await supabase
      .from('rot_rut_payout_request_items')
      .select('id, requested_amount')
      .eq('request_id', params.requestId)
    if (itemsFetchError) {
      log.warn('failed to fetch items for decided_amount mirror', {
        payoutRequestId: params.requestId,
        message: itemsFetchError.message,
      })
    }
    for (const item of items ?? []) {
      const { error: mirrorError } = await supabase
        .from('rot_rut_payout_request_items')
        .update({ decided_amount: item.requested_amount })
        .eq('id', item.id)
      if (mirrorError) {
        log.warn('failed to mirror decided_amount onto item', {
          itemId: item.id,
          message: mirrorError.message,
        })
      }
    }
  }

  // The request is settled: every OTHER bank row still hinting at it is a dead
  // suggestion. This row's own hint was cleared by the link update above.
  await clearSettledInvoiceSuggestions(
    supabase,
    companyId,
    'rot_rut_payout_request',
    params.requestId,
    { exceptTransactionId: params.transactionId ?? null },
  )

  log.info('rot/rut payout settled', {
    userId,
    payoutRequestId: params.requestId,
    journalEntryId,
    amount,
    fullyPaid,
    transactionId: params.transactionId ?? null,
  })

  return {
    ok: true,
    request: updated as SettledRotRutPayoutRequest,
    journalEntryId,
    amount,
    fullyPaid,
  }
}